This invention relates to methods for pressure bonding members of dissimilar metals or the same metal by utilizing eutectic reaction, and more particularly to a method for pressure bonding members or aluminum and copper by utilizing eutectic reaction.
In one type of method for bonding members of dissimilar metals known in the art, diffusion is utilized for effecting bonding of the members. In diffusion bonding, the members to be bonded are brought into contact with each other and heated at a suitable temperature lower than the melting point temperatures of the dissimilar metals, so as to effect diffusion of elements and molecules.
Diffusion bonding is based on the diffusion of the elements and molecules. Thus the condition of the contacting surfaces of the members to be bonded is an important factor in effecting bonding. To be more specific, it is essential that the contacting surfaces are scrupulously clean and free from oxides and other surface contamination. Meeting the aforesaid requirement in diffusion bonding means the provision of a solution to an important problem. It is not too much say that this is the determining factor in effecting diffusion bonding successfully.
As a means for solving the aforesaid problem in diffusion bonding, a method has been developed in which at least one projection is formed on the contacting surface of one member and force fitted in the contacting surface of the other member to be bonded to the one member. When the members to be bonded are formed of aluminum and copper, the projection is generally formed on the member of copper, and the member of aluminum is heated to a temperature lower than the melting point temperature of aluminum when the projection is force fitted in the contacting surface of the member of aluminum. It is to be noted that this method is not essentially a method intended to removed oxides and other surface contamination from the contacting surfaces of the members to be bonded. This method aims at imparting a mechanical bonding force to the contacting surfaces of plastic deformation to which the members to be bonded are subjected when the projection on one member is force fitted in the other member. This method has not yet provided a satisfactory solution to the aforesaid problem because the joint formed by this method has subsequently ruptured at the bond in tension tests conducted on the bonded members.